Switch mechanism



March 194m w. c. FURNAS 2,193,126

' I SWITCH MECHANISM Filed April 22, 193'? 2 Sheets-Sheet 1 gr?" H I INVENTOR.

ATTORNEY.

March 12, 1940. 5 w FURNAS 2,193,126

SWITCH MECHANISM Filed April 22, 195'! Y 2 Sheets-Sheet 2 INVETR. BY wmWfl ATTORNEY iii Patented Mar. 12, 1940 UNITED STATES PATENT OFFICE 3 Claims.

My present invention relates in general to improvements in the art of utilizing fluid under pressure to actuate the control-mechanism for a pressure generating system, and relates more specifically to improvements in the construction and operation of pressure actuated switch mechanisms and unloading devices operable in con- Junction therewith.

\ Generally defined, an object of the present invention is to provide improved electric switch mechanism which is simple and compact in construction, and which is also highly efllcient in operation.

Some of the more specific objects of my invention are as follows:

To provide an improved pressure actuated switch assemblage which is extremely compact and durable in construction, and which is moreover sensitive and precise in operation.

To provide-a new and useful fluid pressure operated switch of the multiple contact type, wherein the closing pressure on the several contacts is effectively equalized and distributed.

To provide a switch assembly in which the various movableelements are most eflectively relieved of excessive friction, and wherein relatively small plural springs are utilized to insure most efilcient functioning oi! the switch.

To provide a switch especially adapted to control the operationol' a pressure producing pump or compressor, and which is adapted to control the range of fluid pressure variation with the utmost precision.

To provide an improved pump unloading assemblage cooperable with a switch for controlling the operation of the motor for driving the pump.

To provide an improved unloading device which is effectively cooperable with electrical systems operable with difierent voltages, as for instance, either with 110 or 220-volts.

To provide a compact and highly efllcient electromagnetically actuated unloader for a motor driven compressor or the like, which will automatically unload the compressor upon interruption for any reason of the motor energizing current.

To provide an improved combined switch and unioader unit which is extremely compact and all portions of which are conveniently accessible but thoroughly protected and concealed during normal operation and use.

To provide improved diaphragm structure for transmitting variations in fluid pressure to switch actuating mechanism.

To provide improved pressure actuated control mechanism, the main parts of which may be manufactured with the aid of punches and dies and thereafter readily assembled to produce final durable assemblages which may be sold at moderate prices.

These and other specific objects and advantages will be apparent from the following detailed description.

A clear conception of embodiments of the various features constituting the present invention, and-of the mode of constructing and of operating switch and unloading mechanisms built in accordance with the improvement, may be had by refqrring to the drawings accompanying and forming a part of this specification wherein like reference characters designate the same or similar parts in the several views.

- Fig. l is a transverse central vertical section through a fluid pressure actuated multiple contact electric switch, showing the actuating mechanism in neutral position and the contacts closed; 1

Fig. 2 is a longitudinal vertical section through the switch actuating mechanism oi! Fig. 1, a part of the section being taken centrally through the housing and fluid pressure mechanisms, andthe switch mechanism being shown in elevation;

Fig. 3 is a transverse horizontal section through the switch actuating mechanism, the main closure cover having been omitted;

' Fig. 4 is a side view of the switch and switch actuating mechanism, looking towardthe pressure range adjusting structure; v

Fig. 5 is a part sectionaltront elevation of the switch contact assembly, showing one of the contact membersclosed and the other open;

Fig. 6 is a lull top view oi. the improved switch contact assemblage, with the cover plate removed; Fig. 'l is a plan view of the diaphragm protecting plate;

Fig. 8 is a diagram showing one of theimproved switches and a magnetically actuated unloader, applied to a fluid pressure supply system;

Fig. 9 is a transverse vertical section through a combined switch and unloader unit, the latter being of the magnetically actuated type;

Fig. 10 is a top view of the unit of Fig. 9 with the cover removed from the magnetic unloader; and

Fig. 11 is a wiring diagram for the switch and magnetic unloader, showing the same cooperating with a 220 volt motor, instead of a volt motor as in Fig. 8.

While the invention has been shown and dcscribed herein as being embodied in an air pressure operated switch and compressor unloader of the multiple contact type, it is not the intent to thereby unnecessarily restrict the scope, since some of the novel features may obviously be applied to other types of switch mechanisms operable with other fluids.

Referring specifically to Figs. 1 to 7 inclusive of the drawings, the improved pressure actuated switch shown therein comprises in general a main cup-shaped lower casing l4 having a substantially central opening in the bottom thereof normally sealed by a flexible rubber diaphragm l3 provided at its top with a reenforcing plate l3 and with a central U-shaped motion transmitting pointed member II; a main horizontal lever I! having medial recesses l3 coacting with the points of the member I! and being fulcrumed at one end on hardened bearing blocks 23 secured to the opposite side walls of the frame 2|; a pair of similar laterally spaced vertical compression springs 22 coacting with the other swinging end of the lever i3 so as to constantly urge the recesses i3 against the points of the member I! in opposition to the action of the diaphragm l3; a substantially horizontal tension spring 23 having one end detachably connected to upstanding ears 24 at the swinging end of the lever H by means of a pin 23 and having its opposite end attached to the swinging end of atoggle striker plate 26 which is fulcrumed in other bearing blocks 21; a pair of contact carriers 23 slidably supported in a contact carried block 23 and having lower ends engageable by the toggle striker plate 23, these carriers 23 also having movable upper contacts 33 adapted to engage fixed contacts 3| secured to the block 23; mechanism for adjusting the tension of the springs 22 and the range of travel of the striker plate 26; and suitable closures including a top cover 32 and a lower plate 33, the latter having a central threaded pipe connection cooperating therewith to provide a diaphragm chamber 33.

The main lower casing |4 may be formed of a single sheet of relatively heavy sheet metal, and has several side openings adapted for the reception of conventional bushings 34; and the diaphragm i3 which is formed of flexible material such as rubber, is clamped between the casing l4 and the lower plate 33 so as to provide the hermetically sealed diaphragm chamber 33 which is in constant open communication through the threaded connection with a fluid pressure supply pipe 36, see Figs. 1 and 2. The diaphragm plate l6 may-also be constructed of sheet metal and the upstanding pointed portions of the member I! extend vertically through a central hole in the base plate 31 of the frame 2|. In order to prevent the rubber diaphragm |3 from sticking in contact with fluid pressure supply port in the lower plate 33, I provide a thin metal plate 33 such as shown in Figs. 1, 2 and 7 which may be readily lifted by the fiuid pressure, but which also prevents the diaphragm i3 from directly engaging the threaded pipe connection of the plate 33. The main lever l3 which is preferably formed of sheet metal has a relatively wide central fulcrum portion which engages the bearing blocks 23 on the upstanding side walls of the frame 2| and the central portion of the plate or lever i3 is open so as to prevent interfering with the movement of 'the spring. 23.

The upper ends of the vertical compression springs 22 react against a transverse horizontal fiat bar 33 which is vertically adjustable to vary the spring tension, by means of an adjusting screw 43, the lower portion of which has screw thread coaction with a central threaded hole in the bar 33, and the upper end of which is provided with a Journal collar 4| rotatably engaging the central portion of a fixed inverted U-shaped sheet metal bracket 42 formed integral with or attached to the frame 2|, as shown in Figs. 1 and 2. This screw 43 is adapted to predetermine the maximum pressure at which the switch mechanism will operate, and the top cover 32 may be provided with a hole in line with the screw 43 so as to permit external adjustment, and is detachably secured to the medial upper portion of the stationary bracket 42 by means of a screw 43. The space within which the springs 22 are confined, may also be segregated from the space in which the electrical contacts 33, 3| are located, by means of a guard plate 44 formed of insulating material and integral with the block 23 which is also formed of insulating material.

As previously indicated, one end of the tension spring 23 is attached to the ears 24, midway between the compression springs 22, by means of a retainer pin 23, and the opposite end of this tension spring coacts with a knife edged opening at the medial portion of the swinging end of the toggle or striker plate 26, as clearly shown in Figs. 1 and 3, so that the tension spring 23 is capable of throwing the plate 26 either above or below the central plane of the toggle. The fulcrumed end of the plate 23 is provided with two spaced knife edges 43 which coact with V-grooves formed in the bearing blocks 21, these blocks being fixedly secured to the fixed bracket 42 as indicated in Figs. 1, 3 and 4; and at least one side of the toggle plate 26 is provided with an integral outwardly extending projection 46 which is engageable with an adjustable side lever 41. The lever 41 is swingable for adjustment about a pivot 43 by means of a vertically adjustable block 43 coacting with the rounded end 33 of the lever 41, and the block 43 also coacts with the screw threaded medial portion of an upright spindle 3| shown in Figs. 2, 3 and 4. The spindle 3| is journaled in an upper bearing 33 at one side of the fixed bracket 42, and has its lower cylindrical portion fitted in a spring clip 32 which forms a stop for limiting the downward travel of the block 43 along the screw threads so as to insure proper functioning of the toggle plate 26. The block 43 is guided between and is prevented from rotating by the casing 2| and bracket 42, and the portion 34 directly beneath the bearing 33 is preferably polygonal. An inverted U-shaped spring member 33 is cooperable with the flat faces of the portion 34 to lock the spindle 3| in adjusted positions, while permitting rotation thereof for purposes of adjustment, and the spindle is accessible for rotation upon removal of the cover 32. Adjustment of the lever 41 about its pivot pin 43 with the aid of the spindle 3i and block 43 obviously serves to vary the limit of swing of the plate 26.

The bearing blocks 21 which are secured to the frame bracket 42 have small abutments 33 as shown in Fig. 3 for preventing sidewise shifting of the plate 26, and as heretofore indicated, the swinging portion of the striker plate 23 is adapted to impinge against the contact carriers 23 to open the switch, see Figs. 1 and 4. The plate 23 is adapted to strike both of the contact carriers simultaneously, so as to insure simultaneous making and breaking of all contacts, and the contacts 33, 3| are formed of suitable material such dis arcane as silver. The upward swinging motion of the plate 28 is arrested 'by a stop 51 secured to or formed integral with one side wall of theirame 22, and the movable contacts 88 of each set are mounted upon a diagonal plate 88 detachably secured to the upper end of the adjacent contact carrier 28 by means of a retaining pin 58. Each of the diagonal contact supporting plates 88, is constantly urged towardclosed position by means of a compression spring 88 coacting therewith in line with its carrier 28, and reacting against a socketed top plate 8| formed of insulating material and detachably secured to the carrier block 28 by screws 82. The block 28 is firmly attached to the side walls 01 the main frame 2| in any suitable manner, and this block with its guard wall N cooperates with the top'plate 8| to house, protect and segregate the contacts 30, 8|. The fixed contacts 3| are firmly attached to the insulating mounting block 28 by means 0! screws 88 and are provided with terminal posts 84 to which the terminals 65 may be attached as depicted in Fig. 1; and the terminal space is preierably segregated from the space within which the switch mechanism is confined, by means of a removable protecting shield 86.

It isalso desirable to provide some kind of compressor unloading means when switch mechanism of the improved type is used to control the operation of electric motor driven compressors, and such unloading may be accomplished either mechanically or electrically, but the unloader should preierably'constitute an integral part of the switch unit. In Figs. 2 and 3. I have illustrated an improved mechanical unloader comprising a lever projection 61 formed integral with the impact plate 26 and having its outer end cooperable with the stem 68 and adapted to actuate an unloading valve 68 which is confined within a fitting 18 secured to a side of the main casing II. The projection 81 is obviously adapted to lift the unloading valve 88 against fluid pressure and the action of the compression spring II, when the impact plate 28 moves the contacts 88, 8| to open position so as to .stop the motor which drives the compressor or pump. The fitting 18 may be provided with a connection I8 communicating with the compressor, and with another connection 12 ordinarily leading to the atmosphere, so that when the unloading valve is opened by elevation of the lever 61, the compressor will be automatically unloaded preparatory to restarting 0! its driving motor.

In Figs. 8 to 11 inclusive, I have disclosed another type 01' unloader which is operable electri-' 'cally and which may also constitute an integral part of the switch unit. In this embodiment of my invention, the switch mechanism is essentially the same as previously described, with the exception that the lever 81 is omitted, and casing I4 and cover 32 are somewhat enlarged to provide an auxiliary unloader chamber between the main switch and the fitting 18. Located with-' in this auxiliary chamber is an electro-magnet comprising a coil 14, the opposite terminals of which are adapted to be connected to the two medial fixed contacts 31 of the main switch, and having a laminated fixed core 15 cooperable with a laminated pivotally suspended armature bar I6. The armature bar 16 is swingably suspended from the magnet supporting frame 11 by means.

of a pivot pin 18 and is urged out of engagement with the core I5 by a tension spring 18. The swinging end of the bar 16 also has a projection 88 which is engageable with the stem 68 of an unloading valve housed within the concealing fitting 18 in the manner previously described.

By, referring to the diagram of Fig. 8, which shows my improved pressure switch and magnetically actuated unloading unit applied to a typical air pressure system, it will be apparent that the compressor driving motor 81 is connected through the'flxed switch contacts ii to the main line 82, and is adapted to propel a compressor 88 which normally delivers air past a non-return valve 84 to a storage reservoir 88. The storage reservoir communicates with the diaphragm I! at all times through the pipe 88, and the unload ing valve 68 is spring pressed and communicates through the connection 18 with the compressor discharge pipe 81 in advance of the non-return valve 84 so as to adapt the valve 68 for compressor unloading purposes. I

In the 110-vo1t circuit of Fig. 8, the motor winding 88 has two leads connected directly to the adjacent fixed contacts II as shown; but in the 220 volt system of Fig. 11, the motor winding 88 has an extra lead 80 which is connected to the terminal post 9| of the electro-magnet. The same switch and unloading mechanisms may thus be utilized for either 110 or 220 volt circuits.

During normal. operation of the improved switch mechanism, and assuming the switch to be applied to a typical fiuid pressure system such as shown in Fig. 8 in conjunction with either type of unloader, the set screw 48 must first be adjusted to cause the contacts 88, II to separate or open when a predetermined maximum pressure of, say, one hundred pounds per square inch is attained in the storage reservoir 88, and the spindle 5! should be set to cause the contacts 28 to close when the pressure in the reservoir has dropped to a predetermined minimum of, say, eighty pounds per square inchl The pressure range will then be twenty pounds. and the high and low limits may obviously be fixed at any predetermined value by proper adjustment oi the screw 48 and sp ndle 5|. When the maximum pressure has been reached in the system, and the switch is open, the toggle plate 26 will be in the position indicated in dot-and-dash lines in Fig. 1, that is, in engagement with the extreme lower ends of the contact carriers 28, the spring 22 serving to retain the plate 28 and the movable contacts 88 in open position. The unloading valve 68 will then be open so as to unload the compressor 83 and to permit easy starting thereof by the motor 8|. i

As the pressure in the reservoir 85 and in the pipe 88 and chamber is reduced, the diaphragm l5 will move downwardly thereby causing the main springs 22 to force the main lever l8 in a downward direction. As thisreduction in fiuid pressure continues, the main lever i8 will eventually carry the end of the spring 28 across the center of the toggle of which the plate 28 constitutes one element, and the spring 28 will then become quickly effective to swing the toggle plate 26 downwardly against the adjusting lever 41. when this action takes place, the compression spring 50 quickly becomes effective to move the diagonal plates 58 and the movable contacts 38 and carriers 28 which are associated with there plates toward closed position, thereby quickly moving the contacts 30 into engagement with the fixed contacts 31 thus completing the electrical circuit. This completion of the electrical circuit will'againstart the motor 8| and the compressor 83 and will eventually cause restoration of the pressure in the reservoir 85.

As the pressure within the reservoir 05 and in the pipe 36 and chamber 35 again reaches the maximum predetermined pressure, the diaphragm I I will have moved the lever l8 upwardly so as to carry the swinging end of the spring 23 upwardly across the central plane of the toggle.

The spring 23 will then become efl'ective to quickly snap the toggle plate 26 into its upper extreme position, and the plate 26 will strike against the lower ends of both of the contact carriers 28,, thereby opening the switch and restoring the parts to contact open' position. While Fig. 5 illustrates one set of contacts 30 as being open while the other is closed, this condition never actually exists, since the striker plate 26 always cooperates with both carriers 28.

The insulating block 29 with its walls H, and the formation of the carriers 28 and plate 6| of insulating material, serve to prevent short cir-' cuiting and possible damage by flashing, and the contacts 30 are formed of suitable material which when engaging the fixed contacts 3|, will insure most eiiective electrical connections without melting or burning. The protecting plate 86 disposed in advance of the terminal bushing 34 prevents the terminals $5 from engaging the switch mechanism, and the top cover 82 is readily removable to permit inspection of the mechanism and easy adjustment of the pressure ranges. The diaphragm protecting disk 38 also prevents the diaphragm I! from sticking to and sealing the air admission and exhaust opening in the plate 33, thus insuring effective operation at all times. By utilizing two relatively light main springs 22 disposed on opposite sides of the toggle actuating spring 23, a simple and more compact and flexible mechanism results, and the tension of the springs 22 may obviously be quickly changed from the exterior of the housings by manipulating the adjusting screw 40. The adjustable spindle 5i provides simple and readily manipulable means for varying the pressure range under which the switch mechanism will operate, and by virtue of the fact-that practically all of the essential portions of the mechanism are formed of sheet metal, the assemblage can be readily produced with punches and dies at minimum cost.

When a mechanical unloader such as shown in Figs. 2 and 5 is employed, the unloading projection 61 will cooperate with the impact plate 26 is attained and the switch is open, the projection 81 will lift the unloading valve 69 through the stem. 63, and will thereby permit escape of the fluid pressure from the pipe line 12 to the atmosphere. Since the plate 26 and projection I! are entirely enclosed within the switch casing, and the operating end oi the projection 81 is entirely concealed within the fitting 10, the unloading mechanism constitutes an integral part of the switch unit and cannot be tampered with. The spring H aids the fluid pressure in seating the valve 69, and when the projection 61 of the plate 28 engages the pin 68, the valve 89 is forced open against the spring and fluid pressure so that unloading will be quickly eifected when the switch is open. 1

The magnetically actuated unloading mechanism of Figs. 8 to 11 inclusive, is adapted to function when the circuit is broken by operation of the switch, or when the electrical line is interrupted in any manner so as to stop the operation of the motor 8|. In this magnetically actuated unloading device, the valve 80 is adaptso that when the desired maximum pressure ed to open against spring and fluid pressure when, the projection ID of the armature bar II engages the stem 88, and the armature bar II will be pulled away from the core ll of the magnet, by the spring 1!, whenever the electrical circuit is broken and the coil 14 is de-energized. As soon as the switch is closed, the armature bar 18 will be drawn into contact with the core 68 against the action of the spring I, and will thereby permit closing of the unloading valve 88. This magnetic unloader likewise constitutes an integral part of the switch mechanism, and all portions of the switch and of the unloading device are again thoroughly concealed and protected.

From-the foregoing specific description of the construction and operation of my improved switch and unloading mechanism, it will be apparent that the present invention provides a switch assembly of simple construction which is highly efllcient in actual, operation. The improved pressure actuated switch functions positively and with extreme accuracy, and may be conveniently adjusted to operate within any desired pressure ranges. The improved unloading mechanisms constituting an integral part of the switch unit, provide an extremely compact assemblage, all elements of which .are effectively protected against tampering. While the improved switch is especially adapted to control the operation of a motor driven compressor, the switch itself may be utilized for other purposes and in any system wherein it is desirable to control the range, of fluid pressure. operations with utmost precision. The fulcrum blocks 20, 21 and the knife edges coacting therewith eliminate friction losses and avoid necessity of lubrication, and the same is true of the knife edges of the member I! coacting with the recesses IS. The improved switch assembly may obviously be manufactured at moderate cost and has proven highly successful in actual commercial use, and the unit is also adapted for use in circuits having different voltages.

It should be understood that it is not desired to limit the present invention to the exact details of construction and to the precise mode of operation herein shown and described, for various modifications within the scope of the claims may occur to persons skilled in the art.

I claim:

1. In combination, a diaphragm movable by fluid pressure, .a main toggle lever movable by said diaphragm, a plate having surface contact with said diaphragm, and being provided with rigid laterally spaced knife edge projections engaging said lever, a spring coacting with each side of said lever approximately in the plane of the corresponding knife edge projection, a pressure equalizing cross bar coacting with both of said springs, adjusting means coacting with said bar midway between said springs for causing the latter to exert equal pressures against said lever in the planes of said knife edge projections,

relatively movable switch contacts, and another toggle lever operable by said main lever to actuate said contacts.

2. In combination, a diaphragm movable by fluid pressure, a frame having a base adjacent said diaphragm and side wall formed integral with the base, a main toggle lever fulcrumed on the front portions oi said walls and being movable by said diaphragm, a rigid plate having surface contact with said diaphragm and being provided with integral laterally spaced knife edge projections ensasins the bottom of said lever. a compression'spring coacting with the top of each side or said lever approximately in the plane of the corresponding knife edge projection, a pressure equalizing bar coacting with both of said springs, an adjusting screw coacting with said bar so as to equalize the pressures on said springs, and on said projections, relatively movable switch contacts carried by said frame, and another toggle lever fulcrumed on the rear portions ,of said walls and cooperating with said main lever to actuate said contacts.

3. In combination, a diaphragm movable by fluid pressure, a frame having a base adjacent said diaphragm .and side wall formed integral with the base, a main toggle lever fulcrumed on the front portions of said walls and bein movable by said diaphragm, a rigid plate havsion springs.

ing surface contact with said diaphragm and being provided with integral laterally spaced knife edge projections engaging the bottom or said lever, a compression spring coacting with the top of each side of said lever approximately in the plane of the corresponding knife edge projection, a pressure equalizing bar coacting with both of said springs, an adjusting screw coacting with said bar so as to' equalize the pressures on said springs, and on said projections, relatively movable switch contacts carried by said frame,another toggle lever fulcrumed on the rear portions of said walls and cooperating with said main lever to actuate said contacts, and a tension spring coacting with the swinging ends of said levers midway between said compres- WIUJAM C. FURNAS. 

